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POV-Ray

The Persistence of Vision Ray Tracer, or POV-Ray, is a ray tracing program which generates images from a text-based scene description, and is available for a variety of computer platforms. It was originally based on DKBTrace, written by David Kirk Buck and Aaron A. Collins for the Amiga computers. There are also influences from the earlier Polyray[5] raytracer contributed by its author Alexander Enzmann. POV-Ray is free and open-source software with the source code available under the AGPLv3.

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Sometime in the 1980s, David Kirk Buck downloaded the source code for a Unix raytracer to his Amiga. He experimented with it for a while, eventually deciding to write his own raytracer, named DKBTrace after his initials. He posted it to the "You Can Call Me Ray" bulletin board system in Chicago, thinking others might be interested in it. In 1987, Aaron A. Collins downloaded DKBTrace and began working on an x86-based port of it. He and David Buck collaborated to add several more features. When the program proved to be more popular than anticipated, they could not keep up with demand for more features. Thus, in July 1991 David turned over the project to a team of programmers working in the GraphDev forum on CompuServe. At the same time, he felt that it was inappropriate to use his initials on a program he no longer maintained. The name "STAR" (Software Taskforce on Animation and Rendering) was considered, but eventually the name became the "Persistence of Vision Ray Tracer", or "POV-Ray" for short, inspired by Dali's The Persistence of Memory.[6][7]

image format support for textures and rendered output, including TGA, PNG, JPEG among others

extensive user documentation

One of POV-Ray's main attractions is its large collection of third party support. A large number of tools, textures, models, scenes, and tutorials can be found on the web. It is also a useful reference for those wanting to learn how ray tracing and related geometry and graphics algorithms work.

POV-Ray, in addition to standard geometric shapes like tori, spheres and heightfields, supports mathematically defined primitives such as the isosurface (a finite approximation of an arbitrary function), the polynomial primitive (an infinite object defined by a 15th order or lower polynomial), the julia fractal (a 3-dimensional slice of a 4-dimensional fractal), the superquadratic ellipsoid (intermediate between a sphere and a cube), and the parametric primitive (using equations that represent its surface, rather than its interior).

POV-Ray internally represents objects using their mathematical definitions; all POV-Ray primitive objects can be described by mathematical functions. This is different from many 3D computer modeling packages, which typically use triangle meshes to compose all objects.

This fact provides POV-Ray with several advantages and disadvantages over other rendering / modeling systems. POV-Ray primitives are more accurate than their polygonal counterparts. Objects that can be described in terms of spheres, planar surfaces, cylinders, tori and the like are perfectly smooth and mathematically accurate in POV-Ray renderings, whereas polygonal artifacts may be visible in mesh-based modeling software. POV-Ray primitives are also simpler to define than most of their polygonal counterparts. In POV-Ray, a sphere is described simply by its center and radius; in a mesh-based environment, a sphere must be described by a multitude of small polygons.

On the other hand, primitive-, script-based modeling is not always a practical method to create objects such as realistic characters or complex man-made artifacts like cars. Those objects have to be created in mesh-based modeling applications such as Wings 3D or Blender and then converted to POV-Ray's own mesh format.

The following is an example of the scene description language used by POV-Ray to describe a scene to render. It demonstrates the use of a background colour, camera, lights, a simple box shape having a surface normal and finish, and the transforming effects of rotation.

POV-Ray image output based on the script to the left

#version3.6;//Includes a separate file defining a number of common colours#include"colors.inc"global_settings{assumed_gamma1.0}//Sets a background colour for the image (dark grey)background{colorrgb<0.25,0.25,0.25>}//Places a camera//direction : Sets, among other things, the field of view of the camera//right: Sets the aspect ratio of the image//look_at: Tells the camera where to lookcamera{location<0.0,0.5,-4.0>direction1.5*zrightx*image_width/image_heightlook_at<0.0,0.0,0.0>}//Places a light source//color : Sets the color of the light source (white)//translate : Moves the light source to a desired locationlight_source{<0,0,0>colorrgb<1,1,1>translate<-5,5,-5>}//Places another light source//color : Sets the color of the light source (dark grey)//translate : Moves the light source to a desired locationlight_source{<0,0,0>colorrgb<0.25,0.25,0.25>translate<6,-6,-6>}//Sets a box//pigment : Sets a color for the box ("Red" as defined in "colors.inc")//finish : Sets how the surface of the box reflects light//normal : Sets a bumpiness for the box using the "agate" in-built model//rotate : Rotates the boxbox{<-0.5,-0.5,-0.5>,<0.5,0.5,0.5>texture{pigment{colorRed}finish{specular0.6}normal{agate0.25scale1/2}}rotate<45,46,47>}

The following script fragment shows the use of variable declaration, assignment, comparison and the while loop construct:

The POV-Ray program itself does not include a modeling feature; it is essentially a pure renderer with a sophisticated model description language. To accompany this feature set, third parties have developed a large variety of modeling software, some specialized for POV-Ray, others supporting import and export of its data structures, including the free and open source 3D creation suite Blender.

Official modifications to the POV-Ray source tree are done and/or approved by the POV-Team. Most patch submission and/or bug reporting is done in the POV-Ray newsgroups on the news.povray.orgnews server (with a Web interfacealso available). Since POV-Ray's source is available there are unofficial forks and patched versions of POV-Ray available from third parties; however, these are not officially supported by the POV-Team.

Official POV-Ray versions currently do not support shader plug-ins.[11] Some features, like radiosity and splines are still in development and may be subject to syntactical change.

Originally, POV-Ray was distributed under its own POV-Ray License. Namely, the POV-Ray 3.6 Distribution License[14] and the POV-Ray 3.6 Source License,[15] which permitted free distribution of the program source code and binaries, but restricts commercial distribution and the creation of derivative works other than fully functional versions of POV-Ray.

One of the reasons that POV-Ray was not originally licensed under the free software GNU General Public License (GPL), or other open source licenses, is that POV-Ray was developed before the GPL-style licenses became widely used; the developers wrote their own license for the release of POV-Ray, and contributors to the software worked under the assumption their contributions would be licensed under the POV-Ray 3.6 Licenses.

^Cason, Chris (8 November 2013). "Download POV-Ray 3.7.0". Retrieved 11 November 2013. Starting with version 3.7, POV-Ray is released under the AGPL3 (or later) license and thus is Free Software according to the FSF definition. […] Full source code is available, allowing users to build their own versions and for developers to incorporate portions or all of the POV-Ray source into their own software provided it is distributed under a compatible license (for example, the AGPL3 or – at their option – any later version).